The modern standard for the DSi is not just a "firmware download" but a combination of tools that transform the console.
If you're having trouble updating your firmware using the official method, there are alternative methods available: Nintendo Dsi Firmware Download
: The final official firmware for the Nintendo DSi is version 1.4.5 . Unlike the 3DS, which saw updates as recently as 2023, the DSi reached its "end of life" for software support several years ago. The modern standard for the DSi is not